Bouncy i beam floor

main floor really bouncy in my 15 year old home. Open underneath and has wood ibeam joist construction, approx. 20 foot span with no supporting columns.
What would be the best approach to "stiffening" or "dampening" this floor. I am concerned about marrying or sistering to this engineered beams as that may effect their intended design.

Thanks

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Bouncy i beam floor

In no particular order of recommendation, standard remedies for your situation includes some or all of the following
1) Addition of a beam and quash blocks at appropriate locations
2) Blocking
3) Sheathing the bottom of the TJI's with nominal 1/2" material

Bouncy i beam floor

If you don't mind the beam in the middle like Bondo said, it is cheap, fast, and will kill the problem. The other suggestions will do, too. You could also cut 1/4" (or thicker) plywood and glue/nail it to the joists to box them; stagger your joints on opposite sides, and get 10' plywood if available. Myself, if I did this, I would try two, ten(or 8) foot pieces on one side and a centered, 10' (or 8) on the other side. You're just looking for a boost, not full support. Many ways to do this. j

Bouncy i beam floor

If you add center blocking, do not nail through the main span joist top/bottom chords to fasten, toe-nail instead.

Gary

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Bouncy i beam floor

If the bottom of the joists are not drywalled, they should have minimum 1x3 strapping, not more than 8' spacing, perpendicular to the joists.

Solid blocking, cut to fit snugly between the webs will also help to stiffen the floor.

Whenever I do I joists, I use 1x3 or 4 cross bridging, stapled with medium crown staples, into the joist flanges. This will help with the bounce associated with long spans on I joists. I like to put 2 rows of X-bridging, 4' apart, centered mid span of the joists.

When walking across a floor, joists with large spans will deflect independantly as you move. Bridging helps to unify the joists and make them work together, as a system.

Strapping the bottoms will have a similar effect.

I was goofing around one day and decided to do a mock floor system, using only wood X-bridging to support the floor. No end bearing on the "joists". I then loaded weight in the center of the floor, to show how bridging provides load sharing across the assembly.

Bouncy i beam floor

I had 270 lbs. on the center joist before the assembly failed. The staples pulled through the 1x3 strapping, which had been laying outside of my garage in the rain. Normally, I would use 1x3 or 4 pine, which would have easily held much more weight before failure.

Bouncy i beam floor

Very informative pictures to illustrate the point, and another route to stiffen a floor. Instead of stiffening parallel to the I joists, you are building trusses perpendicular to them, as well as spreading the load from one joist to its neighbors. I think blocking has the same effect, but with more wood, no?

Bouncy i beam floor

Quote:

Originally Posted by jklingel

Very informative pictures to illustrate the point, and another route to stiffen a floor. Instead of stiffening parallel to the I joists, you are building trusses perpendicular to them, as well as spreading the load from one joist to its neighbors. I think blocking has the same effect, but with more wood, no?

Blocking will have the same effect, as well as add a level of fire protection in enclosed ceilings.

Here's why I prefer X-bridging.

When using conventional lumber, I fasten the bottom of the bridging as soon as the decking is completed. As the lumber shrinks, the bridging actually tightens itself against the joist, making an even stiffer assembly over time.

Wood blocking has the potential to check as it shrinks, which can lend to squeeks in the floor, not to mention, it's hard to fit blocks snugly if the joists are cupped or twisted slightly. In addition, I have seen block after block hammered out by mechanical trades to make way for equipment, pipes, wires, etc.

With X-bridging, more often than not, it won't pose an issue with tradesmen.

Bouncy i beam floor

In addition, I have seen block after block hammered out by mechanical trades to make way for equipment, pipes, wires, etc. With X-bridging, more often than not, it won't pose an issue with tradesmen.

•• That is certainly a big benefit. A long-time home builder once told me that he almost quit finishing on a job when some plumbers showed up with a chain saw to work on the lower level. He said what they did to his nice, 2x6 walls nearly brought him to tears.

Bouncy i beam floor

If i wanted to "stiffen" the wooden i beam, how would I do that?
Could I add 3/4"plywood in 8-10' strips and glue and screw to the upper and lower elements of the i beam or should the plywood go in the area between the upper and lower support elements of the ibeam?
FYI, I do not want to use lally columns, etc., structure is stable just noisy